Abstract
Telomeres are nucleoprotein complexes protecting the physical ends of linear eukaryotic chromosomes and therefore helping to ensure their stability and integrity. Additionally, telomeric sequences can be localized in non-terminal regions of chromosomes, forming so-called interstitial telomeric sequences (ITSs). ITSs are traditionally considered to be relics of chromosomal rearrangements and thus very informative in the reconstruction of the evolutionary history of karyotype formation. We examined the distribution of the telomeric motifs (TTAGGG)n using fluorescence in situ hybridization (FISH) in 30 species, representing 17 families of squamate reptiles, and compared them with the collected data from another 38 species from literature. Out of the 68 squamate species analyzed, 35 possess ITSs in pericentromeric regions, centromeric regions and/or within chromosome arms. We conclude that the occurrence of ITSs is rather common in squamates, despite their generally conserved karyotypes, suggesting frequent and independent cryptic chromosomal rearrangements in this vertebrate group.
Highlights
Telomeres are nucleoprotein complexes that protect the physical ends of linear eukaryotic chromosomes, playing a crucial role in maintaining chromosome stability and integrity [1]
In order to test this hypothesis, we reviewed published data on the occurrence of interstitial telomeric sequences (ITSs) and supplemented it with our novel description of ITSs distribution in 13 species of squamates based on fluorescence in situ hybridization (FISH) experiments
FISH with telomeric probe proved to be a valuable tool in revealing the topology of the telomeric motif (TTAGGG)n in the karyotypes of squamate reptiles
Summary
Telomeres are nucleoprotein complexes that protect the physical ends of linear eukaryotic chromosomes, playing a crucial role in maintaining chromosome stability and integrity [1]. In all vertebrates the DNA component of telomeres consists of the non-coding (TTAGGG)n motif [2], which produce long tandem repetitions varying greatly in size between species, individuals and even cell types [3]. The telomeric motif demonstrates a remarkable evolutionary conservation across vertebrate species [4,5]. Shelterin is composed of three proteins (TRF1, TRF2 and POT1) that directly recognize the (TTAGGG)n motif, and are interconnected by three additional proteins (TIN2, TPP1 and Rap1) to form a duplex structure [7] (for a review see [3]). The telomeric motif is synthesized by telomerase, a reverse transcriptase-like enzyme, which contains an RNA subunit and a catalytic protein subunit called telomerase
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